Which one of the following does not increase while moving down the group of the periodic table?

The element which can form an acidic oxide should be the one whose atomic number is:

The element which forms a basic oxide has the atomic number of:

On moving from left to right in a period of the periodic table, the atomic number of elements increases. What happens to the size of atoms of elements on moving from left to right in a period?

Which of the following set of elements is written correctly in the order of their increasing metallic character?